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groingo
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# Posted: 20 Feb 2015 04:28pm - Edited by: groingo
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After five days of side by side comparison with the Tracer 40 amp MPPT controller and the Renogy PWM 30 amp controller regarding voltage and battery amperage input in identical conditions the winner is.........both, that's right, it was a dead heat, neither held an advantage over the other on my 400 watt solar system.
The only thing I can think of is on a larger system the Tracer may have the advantage and it does have more battery conditioning features than my PWM, and we need to remember that the Tracer does charge using PWM which may be why so similar when it came to actual juice going from panels to batteries but that is the reason we would choose one over the other......interesting footnote when I tested the Kid against the PWM......same results.
Would be nice to see a comparison on a larger system, may be a different ball game but on my 400 watt system the Tracer MPPT simply didn't pencil out.
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MtnDon
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# Posted: 20 Feb 2015 05:26pm - Edited by: MtnDon
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Part of the info is missing. What is the PV panel array and how is it configured for both of the CC? Did one reach full battery capacity sooner? And is it possible to measure and compare accurately when we have to compare the equipment operating on different days?
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groingo
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# Posted: 20 Feb 2015 06:01pm
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I ran one controller at a time then switch it off and run the other for a couple minutes and compare numbers, did this over fifty times and the results were virtually identical, this made keeping weather and clouds from becoming a factor and doing it at random eliminated variables.
The panels are set up in parallel.
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MtnDon
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# Posted: 20 Feb 2015 06:29pm - Edited by: MtnDon
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Okay, I see the method.
Also have to remember the batteries themselves limit how much energy can be put into them at any one time; how many watts in total. Those batteries will require the same number of watts to recharge, no matter where the energy is coming from; PWM solar, MPPT solar or a grid tied charger. When comparing PWM and MPPT solar the MPPT should charge more quickly. The greatest difference may be seen at times with cloudy skies. More difference will also be seen when the panel Vmp is much greater than the voltage required to charge the batteries.
That is going to be a difficult test to arrange with all the weather variables added to the variables of use.
Keep in mind that all CC, except the very old and now very cheap things (think harbor freight kits) use PWM technology. PWM is simply a method of adjusting voltage by turning the output on and off rapidly. It still wastes energy that the battery can not absorb.
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groingo
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# Posted: 20 Feb 2015 08:55pm
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Don:
As always I appreciate the input, the key reason of such short test times is to keep as close as possible to same cloud and weather conditions during the test, look at it as kind of a snap shot, then I swap controllers so controller A runs a couple hours and B is tested then B runs a couple hours an A is tested....this information establishes patterns of each controller under the same conditions and paints a good performance comparison picture....patterns are everything.
Keep in mind, the results were not shocking as both controllers do charge using PWM.
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creeky
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# Posted: 21 Feb 2015 09:26am - Edited by: creeky
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groingo your test values of panel output would be best served if you divide your panels into two 200 watt segments and run them side by side. switching back and forth if necessary.
you should see the advantages of mppt clearly first thing in the morning. a time when your batteries need power the most. recharging after the night and in use with the morning activities.
you should also see more of a difference under cloudy skies. try that for a test.
testing in late morning or afternoon, with your small power usage is basically testing batteries that are full. you will find no meaningful data from that experiment.
which water bucket fills a full container faster? a bucket with huge opening or a bucket with a small opening. the result is identical, the container is full. ya?
to test later in the day you need some kind of load on the system to ensure that you are testing the actual output of the panels and not the output needed.
how'd the equalize cycle work out for you?
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MtnDon
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# Posted: 21 Feb 2015 09:59am
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Quoting: MtnDon remember the batteries themselves limit how much energy can be put into them
Groingo, Creeky spelled out what I was getting at in more words... The batteries need to be "hungry" . Splitting the PV panels in two groups with both CC running simultaneously is a better idea, much better than switching back and forth. If the batteries are low enough and the two CC are set the same you should be able to see some difference.
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groingo
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# Posted: 21 Feb 2015 12:08pm
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The tests I have run have ranged from hungry, starving and full and the numbers have been consistent down the line.
To split the panels and run separate feeds gets too costly for 60 feet of cable to use for a few days use.
I think I have gotten the info I need at this point, the picture is very clear and the numbers consistent and reproducecable.
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